The world's first case of AIDS was announced by a California physician in 1981-this disease has now been afflicting humankind for 17 years.

For over a decade people have been depending on medicines that cannot eradicate the disease, and AIDS still continues to proliferate. Nevertheless, today, as we clearly understand how it is transmitted, prevention of AIDS is not difficult.

AIDS, or Acquired Immune Deficiency Syndrome, is developed from infection by the human immunodeficiency virus (HIV). After this pathogen invades the human body, it can infringe upon and ravage the immune system, weakening a person's resistance to disease. This allows opportunistic infections of viruses, bacteria, fungi and protozoa to flourish, and encourages the development of certain forms of cancer, finally leading to death.

It is generally believed that HIV was first passed to human beings by monkeys during the 1970s in Africa, and then spread to Europe, the Americas, Oceania and Asia. In a short few years the whole earth was engulfed. Not a corner escaped untouched.

Epidemiological data indicates that a small minority of people lack a susceptibility to the HIV virus. Chen Hao-yung, head of the National Institute of Preventive Medicine's virology section, says it is currently known that some Caucasians do not easily contract HIV, because their genes lack a particular chemical receptor.

Other than this, the vast majority of people have no resistance to AIDS. Therefore, how to prevent infection is a lesson everyone must learn.

Concerning viruses

One of the reasons AIDS is so frightening is that it is contagious.

Yet it is actually very easy to prevent the transmission of AIDS. "AIDS is much easier to prevent than the enterovirus that was widespread in Taiwan a while back," says Chen Yi-ming, director of National Yangming University's AIDS Prevention and Research Center.

"In all of history, AIDS is probably the most easily preventable communicable disease," states Twu Shiing Jer, director of the Taipei City Bureau of Health.

HIV has tremendous destructive power inside the human body, but this kind of virus is extremely fragile. As soon as it leaves the human body and is exposed to the air, it quickly dies. The AIDS virus can survive for 48 hours in blood, but home cleaning products such as bleach or ethyl alcohol easily kill it.

The method of transmission of AIDS is different from that of other communicable diseases like the common cold or tuberculosis. It cannot be transmitted through the air but only through blood or other bodily fluids. Therefore, unless a wound on the body or a mucus membrane (in the mouth, vagina, anus or eyes) comes in contact with the blood or bodily fluids of a person already infected, it is impossible to contract the virus.

In other words, conversing, shaking hands, hugging, sneezing, sharing tableware, living in close proximity... none of these can infect a person with AIDS. It is not transmitted except through sexual contact, blood transfusions, shared needles or transmission from mother to baby in the womb.

Actually, in terms of sexual transmission, the odds are not stacked equally for men and women. Chen Yi-ming points out that male genitalia are less likely to develop sores, and the mucus membranes in female sexual organs have a larger number of monocytes that are receptive to viruses. In addition, seminal fluid contains more viruses than vaginal fluid. For these reasons, women are more easily infected by men than vice versa.

Can you get it from a kiss?

Because AIDS is transmitted through blood and other bodily fluids, some people wonder, is it possible to catch AIDS from a kiss or a mosquito bite?

Generally speaking, the rate of infection via saliva is very low. Because saliva contains certain antibodies that suppress viruses, there is currently no verifiable evidence that viruses at a low concentration can be transmitted through saliva. However, if there is a wound inside one's mouth, the possibility of transmission is increased.

As for mosquitos, they are simply not capable of transmitting AIDS. The reason is that the HIV virus can only live in the human body and does not survive inside mosquitos. In addition, the amount of blood carried in a mosquito's proboscis when it bites is extremely small, not enough to transmit HIV. "If mosquitos could pass on AIDS," says Twu Shiing Jer, "old people and children would all be susceptible to infection. It wouldn't be limited to young people with a high degree of sexual activity."

In addition to having one's blood tested and avoiding used needles, the most important way to prevent AIDS is safe sexual behavior-a designated sexual partner and consistent use of condoms.

Besides this, one should avoid sharing needles and toothbrushes with others. One must also sterilize needles used for piercing or tattooing, and tweezers used to squeeze pimples.

Infection doesn't equal illness

The HIV virus can remain latent for a period of eight to ten years. During the virus's latent phase, the infected person will show no symptoms. But once someone is infected, they remain so for life, and they can pass the virus on to others. But being infected with HIV does not equal contracting AIDS.

Exactly what condition can be called AIDS? The standard for diagnosing AIDS is the concentration of T4 white blood cells in the blood stream. When the number of these cells, which serve as disease-fighting agents, drops to 200 per cubic millimeter of blood, it signals the onset of the syndrome. (Ordinarily, people will range between 800 and 1200.)

The latency period differs from person to person. Twu Shiing Jer notes that whether symptoms appear early or late is determined by many different factors, including the virulence and quantity of the virus, the strength of the patient's resistance, whether they are receiving treatment, whether they have a balanced nutritional intake, a regular lifestyle and regular exercise, and how much stress is present in their lives.

For this reason, some people have been infected with the virus for more than ten years without developing the disease, while others fall ill immediately after infection. Generally speaking, after 11 years half of those infected with HIV will have developed AIDS. Once the syndrome begins, half of AIDS victims die within three years.

Hopeless no longer

Diseases evolve, and humankind advances. Former director of NTU Hospital Chuang Che-yen observes that when AIDS first broke out, the first group of people to be infected had a higher rate of death, because of lower immunity within their group, or because the disease had a shorter period of latency. Another explanation may be that the disease was more virulent at that time.

A virus lives and dies with its host. After a relatively virulent strain is extinguished along with its host, weaker strains will be left behind. As the potency of the virus was weakened in this way, the latency period for AIDS victims accordingly lengthened.

Especially since drug-cocktail therapy began to be used, the health conditions of AIDS patients have markedly improved.

The drug-cocktail therapy, often referred to in Taiwan as "three-in-one," utilizes a mixture of two nucleoside analog drugs and one protease inhibitor. The former block the virus from invading the cells of the body, while the latter blocks the virus from leaving a cell once it has entered and reproduced.

This three-in-one therapy, a triple mix of medication that constructs a double barrier, cannot absolutely wipe out the HIV virus. Yet it can reduce the quantity of the virus present in the blood stream. Only in the lymph system does a relatively large amount of the virus survive. Not only does this effectively delay the onset of symptoms, but it also decreases the likelihood of passing the virus on to others through the blood.

Currently, the transmission of the AIDS virus has already begun to level off in advanced countries. Chen Hao-yung believes that this is not because of the efficacy of the medicine, but rather because people have learned about the method of transmission. He believes that in Taiwan, education is widespread and the disease is still in its early stages, with a low level of proliferation; there is hope for AIDS prevention.

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The three-in-one "drug cocktail," which is effective in controlling the AIDS virus, is currently the most effective treatment known. (photo by Vincent Chang)